The invention relates to a hollow milling tool in accordance with the preamble of the independent patent claim.
Hollow milling tools of this kind are used for example in the transplantation of tissue pillars. For example cartilage defects are in certain cases nowadays "repaired" at stressed locations, such as e.g. joints, in such a manner that a blind bore is produced at the defect. location which reaches into the subchondral bone. At a less stressed harvest location then a tissue pillar is taken out which consists of bone which is covered with healthy cartilage. This tissue pillar is transported to the defect location and implanted there into the blind bore.
Various instruments have been proposed for the production of the tissue pillar at the harvest location such as e.g. punches or hollow milling tools (in some cases also designated as "crown borers"). A hollow borer of this kind has teeth which are arranged at the front side and which ablate the tissue in the production of the tissue pillar. The ablated tissue can be transported away through the inner space of the hollow milling tool or via the space which surrounds the hollow milling tool.
Bone tissue is ablated in the production of the tissue pillar. In this the tissue heats up in the immediate vicinity of the distal end of the milling tool (chip forming method). On the other hand, the bone tissue contains materials such as e.g. proteins which can stand only a very limited temperature increase because they could otherwise denature. In this, both tissue which is arranged directly outside round about the milling tool can be affected by a temperature increase of this kind as well as tissue which is directly surrounded by the milling tool, thus the tissue pillar or at least parts thereof.